In a mass mailing system, an addressing machine having a plurality of print heads is typically used to print a mailing address on an envelope along with other printed items, such as the postage indicia, return address and promotional messages. Because the size of the envelope may vary, the print head in the addressing machine must be adjusted. Typically, the print heads are mounted on one or more shafts so that the position of the print heads can be adjusted along the longitudinal axis of the shaft, which is substantially perpendicular to the moving direction of the envelope.
As shown in FIG. 1a, the addressing machine 1 comprises an envelope feeder 10 and a printing section 100. The envelope feeder 10 has a driving mechanism 16 for releasing one envelope 14 at a time from a stack 12 to the printing section 100. The printing section 100 has a driving mechanism 20 and a pair of pickup rollers 22 to move the released envelope 14 further along the moving direction 90. While the envelope 14 is moving along the moving direction 90, a plurality of print head assemblies 40 is used to print the printed items on the envelope 14.
A top view of the printing section 100 is shown in FIG. 2. As shown, the printing section 100 has a rack 200 for mounting a plurality of shaft mounts 210. The print head assemblies are mounted on a plurality of shafts 220, which are mounted on the shaft mounts 210. In order to adjust the print head assemblies 40 relative to the moving path 92 of the envelope 14, the print head assemblies 40 can be slid on the shafts 220. Once each of the print head assemblies 40 has been moved to a desired position, it is locked in that position so that the printed items on the envelope 14 can be printed in a designated area in a consistent fashion. Advantageously, the print head assembly 40 comprises a plurality of print heads fixedly mounted on a carriage 50, which is slideably mounted on the shaft 220.
Furthermore, a machine operator should be able to rotate the print head assemblies 40 upward, as shown in FIG. 3, to occasionally clean the print heads on the assemblies.
Thus, it is desirable and advantageous to provide a method and device for locking and unlocking the print head assemblies so that the position of the print head assemblies relative to the moving path of the envelope can be easily changed or adjusted. Furthermore, it is desirable and advantageous to have a reasonably small locking mechanism so that it will not interfere with the operator when the operator adjusts the position of the print head assemblies and when the operator lifts the print head assemblies for cleaning or other maintenance purposes.